Composite Abrasive Particles for Chemical Mechanical Planarization Composition and Method of Use Thereof

ABSTRACT

Chemical Mechanical Planarization (CMP) polishing compositions comprising composite particles, such as ceria coated silica particles, offer low dishing, low defects, and high removal rate for polishing oxide films. Chemical Mechanical Planarization (CMP) polishing compositions have shown excellent performance using soft polishing pad.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 14/993,128 filed on Jan. 12, 2016 which claims priority to U.S.provisional application 62/102,319 filed on Jan. 12, 2015, and62/221,379 filed on Sep. 21, 2015, the entire contents of which isincorporated herein by reference thereto for all allowable purposes.

BACKGROUND OF THE INVENTION

The present invention relates to chemical mechanical planarization(“CMP”) polishing compositions (CMP slurries, CMP composition or CMPformulations are used interchangeably) used in the production of asemiconductor device, and polishing methods for carrying out chemicalmechanical planarization. In particular, it relates to polishingcompositions comprising composite abrasive particles that are suitablyused for polishing patterned semiconductor wafers that composed of oxidematerials.

Silicon oxide is widely used as dielectric materials in semiconductorindustry. There are several CMP steps in integrated circuit (IC)manufacturing process, such as shallow trench isolation (STI),inter-layer dielectric (ILD) CMP and gate poly CMP etc. Typical oxideCMP slurry involves: abrasive, with or without other chemicals. Otherchemicals could be dispersants to improve slurry stability, booster toincrease removal rate, or inhibitors to decrease removal rate and tostop on the other film, for example, SiN for STI application.

Among common abrasives used in CMP slurries, such as silica, alumina,zirconia, titania and so on, ceria is well-known for its high reactivitytoward silica oxide and is widely used in STI CMP slurry for the highestoxide removal rate (RR) due to the high reactivity of ceria to silica.

Cook et al. (Lee M. Cook, Journal of Non-Crystalline Solids 120 (1990)152-171) proposed a ‘chemical tooth’ mechanism to explain thisextraordinary property of ceria. According to this mechanism, when ceriaparticles are pressed onto silicon oxide film, ceria breaks down silicabonds, forms a Ce—O—Si structure and thus cleavage silica from thesurface.

Most of the ceria used in CMP industry are manufactured fromcalcinations-wet milling process. The resulted ceria has sharp edges andvery wide size distribution. It also has very large “large particlecount” (LPC). All of these are believed to be responsible for defectsand low yields, especially scratch after the wafer is polished. This isconfirmed from IC fabs that are suffering from defects with ceria basedslurries.

Besides calcined ceria, some particle companies have commercial productswith colloidal ceria. Colloidal ceria is made from ceria precursor inaqueous system. Compared to calcined ceria (top-down process), colloidalceria is bottom up process. Colloidal ceria has a much narrower sizedistribution and better controlled shapes. However, due to the crystalgrowth habit in aqueous system, colloidal ceria still has sharp edges.LPC of colloidal ceria is comparable to that of calcined ceria.

As the semiconductor technology advances to smaller feature sizes, thespecifications on allowable size and number of defects on post-polishalso become more challenging. Defects typically comprise scratches,slurry residues and residual film residues. The properties of polishingpads critically affect polishing results during chemical mechanicalpolishing (CMP) of integrated circuit substrates. One of the criticalparameters of the CMP pads that defines the performance is pad hardnessor elasticity. It is known that softer pads cause reduced scratches onsurface (e.g. Hsein et al. Microelectronic Engineering, vol 92, 2012, pp19-23). It will therefore be highly beneficial to use softer pads toreduce scratch defects in critical CMP processes such as shallow trenchisolation. However, it is known that softer pads result in lower removalrates (e.g. Castillo-Mejia et al., Journal of Electrochemical Society,Vol. 150 (2), 2003, pp G76-G82). Also it is known that softer pads havean undesirable impact on post-polish topography of patterned wafers(e.g. L. Wu, Journal of Electrochemical Society, Vol. 153 (7), 2006, pp.G669-G676). Because of these limitations of soft pads, STI CMP processis carried out on harder CMP pads such as IC1000 or IC1010. Compensatingfor lower removal rates on soft pads by increasing abrasive particleloading would lead high defectivity. As a result, for criticalapplications such as STI, it is very challenging to achieve acombination of high removal rates, low defectivity and low topography onsoft pad.

Therefore, there are significant needs for CMP compositions, methods,and systems that can offer higher removal rate (especially on softpolishing pad); low dishing and low defects.

BRIEF SUMMARY OF THE INVENTION

Described herein are oxide material CMP polishing compositions, methodsand systems that satisfy the need.

In one embodiment, described herein is a polishing compositioncomprising:

-   -   composite particles comprising core particles with surfaces        covered by nanoparticles;    -   an additive selected from a compound having a functional group        selected from the group consisting of organic carboxylic acids,        amino acids, amidocarboxylic acids, N-acylamino acids, and their        salts thereof; organic sulfonic acids and salts thereof; organic        phosphonic acids and salts thereof; polymeric carboxylic acids        and salts thereof; polymeric sulfonic acids and salts thereof;        polymeric phosphonic acids and salts thereof; arylamines,        aminoalcohols, aliphatic amines, heterocyclic amines, hydroxamic        acids, substituted phenols, sulfonamides, thiols, polyols having        hydroxyl groups, and combinations thereof;    -   a pH-adjusting agent selected from the group consisting of        sodium hydroxide, potassium hydroxide, cesium hydroxide,        ammonium hydroxide, quaternary organic ammonium hydroxide(e.g.        tetramethylammonium hydroxide), and combinations thereof;    -   and    -   the remaining being water;    -   wherein    -   change of size distribution of composite particles under a        disintegrative force is less than 10%;    -   the core particle is selected from the group consisting of        silica, alumina, titania, zirconia, polymer particle, and        combinations thereof; and the nanoparticle is selected from the        compounds of a group consisting of zirconium, titanium, iron,        manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine,        lanthanum, strontium nanoparticle, and combinations thereof; and    -   the polishing composition has a pH of about 2 to about 12;        preferably about 4 to about 10; more preferably from about 4.5        to about 7.5.

In a further embodiment, described herein is a polishing method forchemical mechanical planarization of a semiconductor substratecomprising at least one surface having at least one oxide layer,comprising the steps of:

-   -   a) contacting the at least one oxide layer with a polishing pad;    -   b) delivering a polishing composition to the surface, the        polishing composition comprising:        -   composite particles comprising core particles with surfaces            covered by nanoparticles;        -   an additive selected from a compound having a functional            group selected from the group consisting of organic            carboxylic acids, amino acids, amidocarboxylic acids,            N-acylamino acids, and their salts thereof; organic sulfonic            acids and salts thereof; organic phosphonic acids and salts            thereof; polymeric carboxylic acids and salts thereof;            polymeric sulfonic acids and salts thereof; polymeric            phosphonic acids and salts thereof; arylamines,            aminoalcohols, aliphatic amines, heterocyclic amines,            hydroxamic acids, substituted phenols, sulfonamides, thiols,            polyols having hydroxyl groups, and combinations thereof;        -   a pH-adjusting agent selected from the group consisting of            sodium hydroxide, potassium hydroxide, cesium hydroxide,            ammonium hydroxide, quaternary organic ammonium            hydroxide(e.g. tetramethylammonium hydroxide), and            combinations thereof;        -   and        -   the remaining being water;        -   wherein            -   change of size distribution of composite particles under                a disintegrative force is less than 10%;            -   the core particle is selected from the group consisting                of silica, alumina, titania, zirconia, polymer particle,                and combinations thereof; and the nanoparticle is                selected from the compounds of a group consisting of                zirconium, titanium, iron, manganese, zinc, cerium,                yttrium, calcium, magnesium, fluorine, lanthanum,                strontium nanoparticle, and combinations thereof; and            -   the polishing composition has a pH of 2 to about 12;                preferably about 4 to about 10; more preferably from                about 4.5 to 7.5;    -   and    -   c) polishing the at least one oxide layer with the polishing        composition.

In yet another embodiment, described herein is a system for chemicalmechanical planarization, comprising:

-   -   a semiconductor substrate comprising at least one surface having        at least one oxide layer;    -   a polishing pad; and    -   a polishing composition comprising:        -   composite particles comprising core particles with surfaces            covered by nanoparticles;        -   an additive selected from a compound having a functional            group selected from the group consisting of organic            carboxylic acids, amino acids, amidocarboxylic acids,            N-acylamino acids, and their salts thereof; organic sulfonic            acids and salts thereof; organic phosphonic acids and salts            thereof; polymeric carboxylic acids and salts thereof;            polymeric sulfonic acids and salts thereof; polymeric            phosphonic acids and salts thereof; arylamines,            aminoalcohols, aliphatic amines, heterocyclic amines,            hydroxamic acids, substituted phenols, sulfonamides, thiols,            polyols having hydroxyl groups, and combinations thereof;        -   a pH-adjusting agent selected from the group consisting of            sodium hydroxide, potassium hydroxide, cesium hydroxide,            ammonium hydroxide, quaternary organic ammonium hydroxide            (e.g. tetramethylammonium hydroxide), and combinations            thereof;        -   and        -   the remaining being water;            -   wherein            -   change of size distribution of composite particles under                a disintegrative force is less than 10%;            -   the core particle is selected from the group consisting                of silica, alumina, titania, zirconia, polymer particle,                and combinations thereof; and the nanoparticle is                selected from the compounds of a group consisting of                zirconium, titanium, iron, manganese, zinc, cerium,                yttrium, calcium, magnesium, fluorine, lanthanum,                strontium nanoparticle, and combinations thereof; and            -   the polishing composition has a pH of about 2 to 12;                preferably about 4 to 10; more preferably from about 4.5                to 7.5;    -   wherein at least one oxide layer is in contact with the        polishing pad and the polishing composition.

In yet another embodiment, described herein is a system for chemicalmechanical planarization, comprising:

-   -   a semiconductor substrate comprising at least one surface having        at least one oxide layer;    -   a soft polishing pad; and    -   a polishing composition comprising:        -   composite particles comprising core particles with surfaces            covered by nanoparticles;        -   an additive selected from a compound having a functional            group selected from the group consisting of organic            carboxylic acids, amino acids, amidocarboxylic acids,            N-acylamino acids, and their salts thereof; organic sulfonic            acids and salts thereof; organic phosphonic acids and salts            thereof; polymeric carboxylic acids and salts thereof;            polymeric sulfonic acids and salts thereof; polymeric            phosphonic acids and salts thereof; arylamines,            aminoalcohols, aliphatic amines, heterocyclic amines,            hydroxamic acids, substituted phenols, sulfonamides, thiols,            polyols having hydroxyl groups, and combinations thereof;        -   a pH-adjusting agent selected from the group consisting of            sodium hydroxide, potassium hydroxide, cesium hydroxide,            ammonium hydroxide, quaternary organic ammonium            hydroxide(e.g. tetramethylammonium hydroxide), and            combinations thereof;        -   and        -   the remaining being water;            -   wherein            -   the core particle is selected from the group consisting                of silica, alumina, titania, zirconia, polymer particle,                and combinations thereof; and the nanoparticle is                selected from the compounds of a group consisting of                zirconium, titanium, iron, manganese, zinc, cerium,                yttrium, calcium, magnesium, fluorine, lanthanum,                strontium nanoparticle, and combinations thereof; and            -   the polishing composition has a pH of about 2 to 12;                preferably about 4 to 10; more preferably from about 4.5                to 7.5;    -   wherein at least one oxide layer is in contact with the        polishing pad and the polishing composition.

The polishing composition can further comprise a surfactant and/orbiological growth inhibitors.

Surfactants can be selected from the group consisting of a). non-ionicsurface wetting agents; b). anionic surface wetting agents; c). cationicsurface wetting agents; d). ampholytic surface wetting agents; andmixtures thereof.

The biological growth inhibitors include, but are not limited to,tetramethylammonium chloride, tetraethylammonium chloride,tetrapropylammonium chloride, alkylbenzyldimethylammonium chloride andalkylbenzyldimethylammonium hydroxide, wherein the alkyl chain rangesfrom 1 to about 20 carbon atoms, sodium chlorite, sodium hypochlorite,and combinations thereof.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows the polishing results from slurries having differentparticles.

FIG. 2 shows the polishing results vs (ceria coated silica) solids % onthe removal rate.

FIG. 3 shows the effect of polyacrylic acid (salt) on the polishingresults (Remove Rate (RR) using IC1010 pad).

FIG. 4 shows effect of pH on the polishing results (RR using IC1010pad).

FIG. 5 shows the polishing performance comparison on soft pad (Fujibopad).

FIG. 6 shows TEOS removal rates from slurries having different abrasiveparticles on both hard pad and soft pad.

FIG. 7 shows TEOS removal rates on different pads using slurriescontaining ceria coated silica composite particles.

FIG. 8 shows number of defects on TEOS wafer after polishing withslurries having different abrasive particles on both hard pad and softpad.

FIG. 9 shows number of defects on high aspect ratio process (HARP) filmsafter polishing with slurries having different abrasive particles onIC1010 pad.

FIG. 10 shows the performance on patterned wafer using slurriescontaining ceria coated silica composite particles on both hard pad andsoft pad.

DETAILED DESCRIPTION OF THE INVENTION

CMP compositions (or CMP slurries, or CMP formulations), methods, andsystems disclosed in this invention can offer higher removal rate(especially on soft polishing pad); low dishing and low defects.

Each of the composite abrasive particles has a core particle and manynanoparticles covering the surface of the core particle. The coreparticle is selected from the group consisting of silica, alumina,titania, zirconia, and polymer particle. The nanoparticles are selectedfrom the group consisting of oxides of zirconium, titanium, iron,manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine,lanthanum and strontium nanoparticles.

The amount of nanoparticles covering the surface of the core particlespreferably falls within the following range in terms of the solid weightratio. The solid weight (b) of the nanoparticles relative to the solidweight (a) of the core particles is (b)/(a)=0.01 to 1.5, preferably 0.01to 1.2.

One of the examples of the composite particles is to have silica as thecore particles and ceria as the nanoparticles; and each silica coreparticle has ceria nanoparticles covering its shell. The surface of eachsilica particle is covered by ceria nanoparticles. The silica baseparticles are amorphous; and the ceria nanoparticles are singlycrystalline.

Diameter of the ceria nanoparticles covering the core particle ispreferably greater than 10 nm, preferably more than 13 nm. Having largerceria particle diameter would allow higher removal rate to be possible.

Core particle size may range from 10 nm to 500 nm, preferably between 20nm to 200 nm, most preferably between 50 nm and 150 nm.

Another aspect of the present invention, involves use of ceria coatedsilica particles that do not disintegrate under polishing forces. It ishypothesized that if the particles do not breakdown under the action ofpolishing forces (i.e. disintegrative forces) and keep thecharacteristic of original particle size, then the removal rate wouldremain high. If the particles on the other hand disintegrate underpolishing forces, the removal rate would decrease owing to effectivelysmaller abrasive particle size. Breaking of the particles may also yieldirregular shaped particles which may have undesirable effect onscratching defects. Particle stability under disintegrative forces canalso be determined by subjecting the formulation to the ultrasonicationtreatment for half an hour and measuring the changes in sizedistribution. Preferred conditions for ultrasonication treatment are ½hour immersion in bath with 42 KHZ frequency at 100 W output. Particlesize distribution can be measured by using any suitable technique suchas Disc Centrifuge (DC) method or Dynamic Light Scattering (DLS).Changes in size distribution can be characterized in terms of changes inmean particle size or D50 (50% particles below this size) or D99 (99%particles below this size) or any similar parameters. Preferably thechanges in particle size distribution of ceria coated silica particlesafter ultrasonication treatment is less than 10%, more preferably lessthan 5% or most preferably less than 2%; by using for example DC andmean particle size, D50, D75 and/or D99. Using such stable particles inCMP slurry formulations would allow more effective utilization ofpolishing forces for film material removal and would also preventgeneration of any irregular shapes that would contribute to scratchingdefects

In another aspect of the present invention, the silica-based compositeparticle having an amorphous oxide layer including at least one type ofelement among aluminum, zirconium, titanium, iron, manganese, zinc,cerium, yttrium, calcium, magnesium, fluorine, lanthanum silicon, andstrontium on the surface of an amorphous silica particle A, and acrystalline oxide layer B including at least one type of elementselected from among zirconium, titanium, iron, manganese, zinc, cerium,yttrium, calcium, magnesium, fluorine, lanthanum and strontiumthereupon.

Since advanced CMP applications require extremely low levels of metalssuch as sodium on the dielectric surface after polishing, it is desiredto have very low trace metals, especially sodium in the slurryformulations. In certain preferred embodiments the formulations compriseceria coated silica particles that have less than 5 ppm, more preferablyless than 1 ppm most preferably less than 0.5 ppm of sodium impuritylevels for each percent of particles in the formulations by weight.

The composite particles are used as abrasive in the CMP compositions,formulations or slurries (“CMP composition”, “CMP formulation”, or CMPslurry” are used interchangeably). An example is STI (Shallow TrenchIsolation) CMP formulations, to polish oxide films, such as variousmetal oxide films; and various nitride films. In STI formulations, theformulations comprising silica coated ceria composite particles canprovide very high removal rates of silicon oxide films and very lowremoval rates of silicon nitride polish stop films. These slurryformulations can be used to polish a variety of films and materialsincluding but not limited to thermal oxide, Tetra Ethyl Ortho Silicate(TEOS), High Density Plasma (HDP) oxide, High Aspect Ratio Process(HARP) films, fluorinated oxide films, doped oxide films, organosilicateglass (OSG) low-K dielectric films, Spin-On Glass (SOG), polymer films,flowable Chemical Vapor Deposited (CVD) films, optical glass, displayglass. These formulations can be used in stop-in-film applications,where the polishing is stopped once the topography is removed and a flatsurface is achieved. Alternatively these formulations can be used inapplications that involve polishing the bulk film and stopping at astopper layer. These formulations can be used in a variety ofapplications including Shallow Trench Isolation (STI), Inter LayerDielectric (ILD) polish, Inter Metal Dielectric (IMD) polish, throughsilicon via (TSV) polish. These formulations may also be used in anyother applications such as glass polishing or solar wafer processing orwafer grinding where high removal rates are desired.

The CMP composition comprises composite particles, a pH adjusting agentthat is used to adjust pH of the CMP composition to the optimized pHcondition; a suitable chemical additive to enhance/suppress the removalrate of polish stop layer/film; and the remaining being water.

The abrasive is present in an amount from 0.01 wt % to 20 wt %,preferably, from 0.05 wt % to 5 wt %, more preferably, from about 0.1 wt% to about 1 wt %.

Chemical additive includes, but is not limited to a compound having afunctional group selected from the group consisting of organiccarboxylic acids, amino acids, amidocarboxylic acids, N-acylamino acids,and their salts thereof; organic sulfonic acids and salts thereof;organic phosphonic acids and salts thereof; polymeric carboxylic acidsand salts thereof; polymeric sulfonic acids and salts thereof; polymericphosphonic acids and salts thereof; arylamines, aminoalcohols, aliphaticamines, heterocyclic amines, hydroxamic acids, substituted phenols,sulfonamides, thiols, polyols having hydroxyl groups, and combinationsthereof.

The amount of chemical additive ranges from about 0.1 ppm to 0.5 wt %relative to the total weight of the barrier CMP composition. Thepreferred range is from about 200 ppm to 0.3% and more preferred rangeis from about 500 ppm to 0.15 wt %.

The pH-adjusting agent includes, but is not limited to, sodiumhydroxide, cesium hydroxide, potassium hydroxide, cesium hydroxide,ammonium hydroxide, quaternary organic ammonium hydroxide (e.g.tetramethylammonium hydroxide) and mixtures thereof.

The amount of pH-adjusting agent ranges from about 0.0001 wt % to about5 wt % relative to the total weight of the CMP composition. Thepreferred range is from about 0.0005% to about 1 wt %, and morepreferred range is from about 0.0005 wt % to about 0.5 wt %

The pH of the CMP composition ranges from about 2 to about 12. Thepreferred range is about 4 to about 10. The most preferred range is fromabout 4.5 to 7.5.

The CMP composition may comprise a surfactant.

The surfactant includes, but is not limited to, a). Non-ionic surfacewetting agents; b). Anionic surface wetting agents; c). Cationic surfacewetting agents; d). ampholytic surface wetting agents; and mixturesthereof.

The non-ionic surface wetting agents include, but are not limited to,oxygen- or nitrogen-containing compounds with various hydrophobic andhydrophilic moieties in the same molecules, the molecular weight rangesfrom several hundreds to over 1 million. The viscosities of thesematerials also possess a very broad distribution.

The anionic surface wetting agents are compounds that possess thenegative net charge on major part of molecular frame. These compoundsinclude, but are not limited to salts with suitable hydrophobic tails,such as alkyl carboxylate, alkyl polyacrylic salt, alkyl sulfate, alkylphosphate, alkyl bicarboxylate, alkyl bisulfate, alkyl biphosphate, suchas alkoxy carboxylate, alkoxy sulfate, alkoxy phosphate, alkoxybicarboxylate, alkoxy bisulfate, alkoxy biphosphate, such as substitutedaryl carboxylate, substituted aryl sulfate, substituted aryl phosphate,substituted aryl bicarboxylate, substituted aryl bisulfate, substitutedaryl biphosphate etc. The counter ions for this type of surface wettingagents include, but are not limited to potassium, ammonium and otherpositive ions. The molecular weights of these anionic surface wettingagents range from several hundred to several hundred-thousands.

The cationic surface wetting agents possess the positive net charge onmajor part of molecular frame. These compounds include, but are notlimited to salts with suitable hydrophobic tails, such as carboxylate,sulfate, phosphate, bicarboxylate, bisulfate, biphosphate, etc. Thecounter ions for this type of surface wetting agents include, but arenot limited to potassium, ammonium and other positive ions. Themolecular weights of these anionic surface wetting agents range fromseveral hundred to several hundred-thousands.

The ampholytic surface wetting agents possess both positive and negativecharges on the main molecular chains and with their relative counterions. Examples of such bipolar surface wetting agents include, but arenot limited to salts of amino-carboxylic acids, amino-phosphoric acid,amino-sulfonic acid, and mixtures thereof.

Examples of surfactants also include, but are not limited to, dodecylsulfate sodium salt, sodium lauryl sulfate, dodecyl sulfate ammoniumsalt, secondary alkane sulfonates, alcohol ethoxylate, acetylenicsurfactant, and any combination thereof. Examples of suitablecommercially available surfactants include TRITON™, Tergitol™, DOWFAX™family of surfactants manufactured by Dow Chemicals and varioussurfactants in SUIRFYNOL™, DYNOL™, Zetasperse™, Nonidet™, and Tomadol™surfactant families, manufactured by Air Products and Chemicals.Suitable surfactants of surfactants may also include polymers comprisingethylene oxide (EO) and propylene oxide (PO) groups. An example of EO-POpolymer is Tetronic™ 90R4 from BASF Chemicals.

Other surfactants that have functions of dispersing agents and/orwetting agents include, but are not limited to, polymeric compoundswhich may have anionic or cationic or nonionic or zwitterioniccharacteristics. Examples are polymers/copolymers containing functionalgroups such as acrylic acid, maleic acid, sulfonic acid, vinyl acid,ethylene oxide, etc.

The amount of surfactant ranges from about 0.0001 wt % to about 10 wt %relative to the total weight of the CMP composition. The preferred rangeis from about 0.001 wt % to about 1 wt %, and more preferred range isfrom about 0.005 wt % to about 0.1 wt %.

Formulations may also comprise water soluble polymers which may compriseanionic or cationic or non-ionic or combinations of groups.

The CMP composition may comprise biological growth inhibitors orpreservatives to prevent bacterial and fungal growth during storage.

The biological growth inhibitors include, but are not limited to,tetramethylammonium chloride, tetraethylammonium chloride,tetrapropylammonium chloride, alkylbenzyldimethylammonium chloride, andalkylbenzyldimethylammonium hydroxide, wherein the alkyl chain rangesfrom 1 to about 20 carbon atoms, sodium chlorite, and sodiumhypochlorite.

Some of the commercially available preservatives include KATHON™ andNEOLENE™ product families from Dow Chemicals, and Preventol™ family fromLanxess. More are disclosed in U.S. Pat. No. 5,230,833 (Romberger etal.) and US Patent Application No. US 20020025762. The contents of whichare hereby incorporated by reference as if set forth in theirentireties.

Formulations of this invention are especially effective on softer padswith better removal rates, defects and planarity compared toformulations with different particles. CMP pads can be characterized forelasticity or hardness using a variety of techniques such as Shorehardness testing, dynamical mechanical analysis, ultrasoniccharacterization, compositional analysis to determine ratio of hard tosoft polymer segments, etc. Shore D hardness testing measured as per themethod described in ASTM D2240-1 0 ASTM standard is a well-known testingmethod for CMP pad hardness. Although there is no clear definition inliterature demarking soft pad and hard pad, CMP pads such as IC1000 andIC1010 (Supplied by Dow Chemicals) which are generally considered hardpads have a Shore D hardness of 57. CMP pads characterized as soft suchas Dow Ikonic 2000 series have Shore D hardness less than 45. Otherexamples of commercially available soft pads include Politex series padsfrom Dow Chemicals, EPIC D200 series pad from Cabot Microelectronics,Fujibo H7000N pads from Fujibo, Nexplanar 11EG from Nexplanar, VP3500pad from Dow Chemicals. While polishing on soft pads, the formulationsof this invention comprising ceria coated silica particles provide atleast 2 times, more preferably more than 5 times, and most preferablymore than 10 times higher removal rates on TEOS films compared tosimilar formulation comprising calcined ceria particles with comparablemean particle size as measured by Disc Centrifuge technique.

Formulations of this invention are especially effective on softer padswith better removal rates, defects and planarity compared toformulations with different particles. CMP pads can be characterized forelasticity or hardness using a variety of techniques such as Shorehardness testing, dynamical mechanical analysis, ultrasoniccharacterization, compositional analysis to determine ratio of hard tosoft polymer segments, etc. Shore D hardness testing measured as per themethod described in ASTM D2240-1 0 ASTM standard is a well-known testingmethod for CMP pad hardness. Although there is no clear definition inliterature demarking soft pad and hard pad, CMP pads such as IC1000 andIC1010 (Supplied by Dow Chemicals) which are generally considered hardpads have a Shore D hardness of 57. CMP pads characterized as soft suchas Dow Ikonic 2000 series have Shore D hardness less than 45. Otherexamples of commercially available soft pads include Politex series padsfrom Dow Chemicals, EPIC D200 series pad from Cabot Microelectronics,Fujibo H7000N pads from Fujibo, Nexplanar 11EG from Nexplanar, VP3500pad from Dow Chemicals. While polishing on soft pads, the formulationsof this invention comprising ceria coated silica particles provide atleast 2 times, more preferably more than 5 times, and most preferablymore than 10 times higher removal rates on TEOS films compared tosimilar formulation comprising calcined ceria particles with comparablemean particle size as measured by Disc Centrifuge technique. The removalrates of TEOS films while polishing at 2 psi downforce on a soft padwith a slurry formulation comprising 0.5 wt % abrasive particles wouldbe higher than 500 Angstroms/min, more preferably more than 750Angstroms/min or most preferably more than 1000 Angstroms/min.

WORKING EXAMPLES

Polishing Pad IC1010 pad, supplied by Dow Corporation; and soft Fujibopolishing pad supplied by Fujibo, were used for CMP process.

TEOS oxide films by Chemical Vapor Deposition (CVD) usingtetraethylorthosilicate as the precursor

HDP oxide films made by high density plasma (HDP) technique

SiN films—Silicon nitride films

Parameters:

Å: angstrom(s)—a unit of length

BP: back pressure, in psi units

CMP: chemical mechanical planarization=chemical mechanical polishing

CS: carrier speed

DF: Down force: pressure applied during CMP, units psi

min: minute(s)

ml: milliliter(s)

mV: millivolt(s)

psi: pounds per square inch

PS: platen rotational speed of polishing tool, in rpm (revolution(s) perminute)

SF: polishing composition flow, ml/min

Removal Rates and Selectivity

Removal Rate (RR)=(film thickness before polishing−film thickness afterpolishing)/polish time.

TEOS RR Measured TEOS removal rate at 2.0 psi (soft pad) and 4.7 psi(hard pad) down pressure of the CMP tool

HDP RR Measured HDP removal rate at 2.0 psi (soft pad) and 4.7 psi (hardpad) down pressure of the CMP tool

SiN RR Measured SiN removal rate at 2.0 psi (soft pad) and 4.7 psi (hardpad) down pressure of the CMP tool

Selectivity of TEOS/SiN=TEOS RR/SiN RR; HDP/SiN=HDP RR/SiN RR at samedown force (psi)

All percentages are weight percentages unless otherwise indicated.

General Experimental Procedure

In the examples presented below, CMP experiments were run using theprocedures and experimental conditions given below.

The CMP tool that was used in the examples is a Mirra®, manufactured byApplied Materials, 3050 Boweres Avenue, Santa Clara, Calif., 95054. AFujibo H7000HN pad, supplied by Narubeni America Corporation, was usedon the platen for the blanket wafer polishing studies. Pads werebroken-in by polishing twenty-five dummy oxide (deposited by plasmaenhanced CVD from a TEOS precursor, PETEOS) wafers. In order to qualifythe tool settings and the pad break-in, two PETEOS monitors werepolished with Syton® OX-K colloidal silica, supplied by Air ProductsChemical Incorporation, at baseline conditions.

The oxide film thickness specifications are summarized below:

TEOS: 15,000 Å

HDP: 10,000 Å

Example 1

Ceria coated silica particles were composite particles that have silicaas the core particle and ceria nanoparticles on the silica particlesurface. LPC (Large particle Count) tells how many big particles in theslurry. As a widely accepted concept, scratch is normally caused by bigparticles. Usually, slurry with higher LPC gives worse performance ondefects compared to slurry with lower LPC. LPCs are typically measuredby optical techniques such as light obscuration or Single ParticleOptical Sizing (SPOS).

Table 1 compared LPC of three different particle solutions usingAccusizer™ 780 particle sizing system: a solution containing calcinedceria particles (Mean particle size by Disc Centrifuge: 97.9 nm), asolution containing colloidal ceria particles (HC90 obtained fromSolvay), and a solution containing ceria coated silica compositeparticles (CPOP-20 from JGC C&C Ltd). CPOP-20 particles are made by themethods described in JP20131191131, JP2013133255, JP2015-169967, andJP2015-183942.

TABLE 1 LPC comparison of different particle solutions particles LPC >=0.51□m (#/ml) LPC >= 1□m (#/ml) Calcined ceria 1.22E+10 9.64E+6 Colloidal ceria 1.62E+11 7.09E+08 Ceria coated silica 2.88E+08 9.50E+05

The solution containing ceria coated silica composite particles had thelowest LPC compared to the other two. This is highly desired for CMPapplications, especially for advanced nodes where the yield is highlysensitive on defects.

Example 2

The CMP compositions comprised 0.5 wt % abrasive, 0.077 wt % ammoniumpolyacrylate (Molecular Weight 16000-18000), ammonium hydroxide, andwater. The CMP compositions had a pH of 5.

All three CMP compositions had the same chemical constitutes, pH andabrasive wt %. The only difference in the three slurries was the type ofabrasives being used. Three types of abrasive were conventional calcinedceria and colloidal ceria, and ceria coated silica (the compositeparticles). The oxide films polished were TEOS films, referring to theoxide film made by CVD (chemical vapor deposition) using TEOS(tetraethyl orthosilicate) as precursor; and HDP (high density plasma)films, referring to oxide films made by HDP technique.

The CMP compositions and IC1010 pad were used to polish the oxide filmsand SiN films.

CMP performance (removal rate-RR and defects) with different abrasiveparticles were compared and shown in FIG. 1. The ceria coated silica hadhighest RR on both TEOS and HDP oxide films. It also had the highestselectivity of oxide film over SiN and a lower defect (threshold at 0.13μm).

Example 3

All CMP compositions had same chemical constitutes, but with differentamount (wt %) of ceria coated silica abrasive. All CMP compositions had0.077 wt % ammonium polyacrylate (Molecular Weight 16000-18000),ammonium hydroxide. The CMP compositions had a pH of 7.

The CMP compositions and IC1010 pad were used to polish the oxide films.

Effect of ceria coated silica abrasive wt % on RR was studied and shownin FIG. 2. When the amount (wt %) of ceria coated silica abrasiveincreased, both TEOS RR and HDP RR increased shown as the solids skew inFIG. 3. As a comparison, SiN RR stayed flat. When 0.5 wt % ceria coatedsilica abrasive was used, TEOS RR and HDP RR reached almost 6,000 Å/min.The result indicates the ceria coated silica particles are veryefficient on oxide film removal.

Example 4

All CMP compositions had same chemical constitutes, but different amount(wt %) of ammonium polyacrylate (Molecular Weight 16000-18000). All CMPcompositions comprised: 0.25 wt % of ceria coated silica as theabrasive, ammonium hydroxide. The CMP compositions had a pH of 5.

The CMP compositions and IC1010 pad were used to polish the oxide films.

The effect of polyacrylate concentration on RR was shown in FIG. 3. Asthe polyacrylic acid (salt) concentration in the CMP compositionsslurries increased from in the range of 0 to 0.30 wt %, RR of TEOS filmand RR of HDP film changed significantly from 3500 Å/min. to ˜500 Å/min.SiN RR changed very little in the range and reached a steady level oncepolyacrylic acid (salt) reached 0.1 wt %. The relative ratio of TEOS RRvs HDP RR also changed in the range. When little amount (0.13 wt %) ofammonium polyacrylate (Molecular Weight 16000-18000) was added, HDP RRwas higher than TEOS RR. After polyacrylate concentration reached acertain level (e.g. ˜0.13% in FIG. 3), TEOS RR turned to be higher thanHDP RR. As comparison, similar test with wt % of polyacrylic acid (salt)vs RR with calcined ceria and colloidal ceria, HDP RR is always lowerthan TEOS RR at any wt % of polyacrylate.

Example 5

All CMP compositions comprised: 0.25 wt % of ceria coated silica as theabrasive, 0.077 wt % of ammonium polyacrylate (Molecular Weight16000-18000), ammonium hydroxide. The CMP compositions had a pH of 5 or7.

The CMP compositions and IC1010 pad were used to polish the oxide films.

The effect of different pH on RR was shown in FIG. 4. As pH increasedfrom 5 to 7, TEOS RR and HDP RR also increased, while SiN RR decreased.Thus, changing pH to neutral would increase the oxide/SiN selectivity.At pH=5, HDP RR was higher than TEOS RR. However, the result wasreversed at pH=7 where TEOS RR being higher than HDP RR.

Example 6

All CMP compositions comprised: 0.5 wt % of ceria coated silica as theabrasive, 0.077 wt % of ammonium polyacrylate (Molecular Weight16000-18000), ammonium hydroxide. The CMP compositions had a pH of 5.

The CMP compositions and a soft pad, e.g. Fujibo pad, were used topolish the oxide films. The results were shown in FIG. 5.

When the oxide films were polished with a soft pad, e.g. Fujibo pad, CMPcompositions with colloidal ceria and calcined ceria had negligibleremoval rate. As a contrast, CMP compositions with ceria coated silicagave very high removal rates. This was a unique performance of the CMPcomposition comprising ceria coated silica composite particles.

Example 7

Three CMP Formulations A, B and C were made with different abrasivematerials. All the formulations comprised 0.5 wt % abrasive particles,0.077 wt % ammonium polyacrylate (Molecular Weight 16000-18000), with pHadjusted between 5 and 6.

Formulation A was made with calcined ceria particles (described inexample 1), formulation B was made with HC-90 colloidal ceria particlesobtained from Solvay Chemicals, and formulation C was made with CPOP-20ceria coated silica particles.

Polishing with these slurries was carried out using different CMP pads,Hard Pad #1 (IC1000 from Dow Chemicals), Soft Pad #1 (Fujibo H7000 fromFujibo), Soft Pad #2 (VP3500 from Dow Chemicals), Soft Pad #3 (Nexplanar11EG from Nexplanar). Polishing on the hard pad was performed with 4.7psi downforce. Polishing on soft pad was performed with 2 psi.

FIG. 6 showed that with ceria coated silica particles (Formulation C)very high TEOS removal rates were achieved on both hard pad and soft pad(#1). With calcined ceria (Formulation A) and colloidal ceria(Formulation B), the TEOS removal rates on soft pads were extremely lowto be effective for CMP application. Ceria coated silica particlesshowed unexpectedly TEOS high rates on soft pad.

Data in FIG. 7 showed TEOS removal rates on different pads usingFormulation C. High TEOS removal rates were achieved using all differenttypes of pads.

Number of defects on TEOS wafer after polishing with Formulations A andC using Hard Pad #1 and Soft Pad #3 were measured. The results wereshown in FIG. 8. Wafers polished with Formulation A on Soft Pad 3 werenot measured for defectivity because very small thickness of filmremoved.

Formulation C containing ceria coated silica particles had dramaticimprovement in defects compared to Formulation A containing calcinedceria even on hard pad.

Defects were also much lower on soft pad compared to hard pad. Usingceria coated silica particles thus enables CMP applications whichrequire polishing on soft pad to achieve both high removal rates and lowdefects.

Number of defects on high aspect ratio process (HARP) films afterpolishing with Formulations A and C using IC1010 pad were measured. Theresults were shown in FIG. 9. The defects using Formulation C containingceria coated silica particles resulted in very low defects compared tothe defects using Formulation A containing calcined ceria particles.

Performance on patterned wafer with Formulation C was also measuredusing both hard pad (IC1010) and soft pad (#3). The results of dishingwere shown in FIG. 10.

Topography on the wafers was measured on 50 micron lines at 50% patterndensity at various polishing times. The results showed very low dishingtopography on 50 micron lines using both soft and hard pads. Dishing isknown to be much worse on soft pad compared to hard pad. Using ceriacoated silica particles allowed low dishing even on soft pads.

Example 8

Three slurry formulations (D,E,F) comprising water, 0.5% abrasiveparticles, 0.077% ammonium polyacrylate (Molecular Weight 16000-18000),ammonium hydroxide to adjust pH to 5 were prepared with differentabrasive particles.

Formulation D was made with ceria coated silica particles (Referred toas Particle CP2) that were prepared as per the method described in US2012/0077419 for comparison. Mean Particle Size (MPS) measured by DiscCentrifuge Analysis was 41 nm. Formulation E was prepared using calcinedceria particles (Mean particle size measured by Disc CentrifugeAnalysis: 97 nm) described in example 1. Formulation F was preparedusing CPOP-20 ceria coated silica particles as described in example 1.Mean Particle Size (MPS) of these particles measured by Disc Centrifugewas 97.7 nm.

These slurry formulations were used to polish TEOS wafers on Bruker CP4Minipolisher. Polishing was performed at 2 psi downforce with 230 RPMtable speed, 87 RPM Head Speed and with 13 ml/min slurry flow rate withFujibo H7000 CMP pad.

Table 2 listed the removal rate data (Angstroms/minute) for each of thethree wafers used per slurry formulation.

TABLE 2 Wafer 1 Wafer 2 Wafer 3 Average Formulation (Å/min) (Å/min)(Å/min) (Å/min) D (Comparative) 10 51 116 59 E (Comparative) 41 22 16 26F 1093 1153 1137 1127

As evidenced from Table 2, Formulation F using CPOP-20 ceria coatedsilica particles outperformed Formulations D and E.

The results showed that the comparative formulations with alternateparticles did not provide necessary removal rates of oxide films on softpad CMP process. Formulations of this invention provide removal rateswhich are greatly higher than the comparative formulations thus enablingCMP of oxide films, especially on soft pads.

Example 9

Dispersions of particles in water were tested for the stability under adisintegrative force, that is under ultrasonic disintegration.

The experiment was performed in Branson 2510R-MI Sonic bath with a 100watt output at 42 KHz. Ceria coated silica CPOP-20 particles asdescribed in example 1 were compared against CP2 particles described inexample 9.

TABLE 3 MPS d50 d75 d99 sample (nm, DC) (nm, DC) (nm, DC) (nm, DC)CPOP-20 97.7 94.7 114.8 172.0 CPOP-20 sonicated 96.7 94.1 114.3 171.1 30min Change % 1.0% 0.6% 0.4% 0.5% CP2 41.1 35.7 45.0 136.4 CP2 sonicated30 min 33.6 30.4 36.7 77.0 Change % 18.2% 14.8% 18.4% 43.5%

The particle size distribution as measured by Disc Centrifuge method(DC24000 UHR from CPS Instruments) before and after ultrasonicationtreatments for CPOP-20 and CP2 particles were shown in Table 3respectively.

The results indicated that the particles used in formulations of thisinvention did not show change in size distribution, indicating a strongbonding between core and the coated particles.

The change in size distribution of CP2 particles was >14%. Data in Table3 also showed that the particle size distribution shifting towardssmaller particles, indicating that composite particles may not bestable, such as the weak bonding between core and the coated particles.

The foregoing examples and description of the embodiments should betaken as illustrating, rather than as limiting the present invention asdefined by the claims. As will be readily appreciated, numerousvariations and combinations of the features set forth above can beutilized without departing from the present invention as set forth inthe claims. Such variations are intended to be included within the scopeof the following claims.

1. A polishing composition comprising: composite particles comprisingcore particles with surfaces covered by nanoparticles; an additiveselected from a compound having a functional group selected from thegroup consisting of organic carboxylic acids, amino acids,amidocarboxylic acids, N-acylamino acids, and their salts thereof;organic sulfonic acids and salts thereof; organic phosphonic acids andsalts thereof; polymeric carboxylic acids and salts thereof; polymericsulfonic acids and salts thereof; polymeric phosphonic acids and saltsthereof; arylamines, aminoalcohols, aliphatic amines, heterocyclicamines, hydroxamic acids, substituted phenols, sulfonamides, thiols,polyols having hydroxyl groups, and combinations thereof; a pH-adjustingagent selected from the group consisting of sodium hydroxide, potassiumhydroxide, cesium hydroxide, ammonium hydroxide, quaternary organicammonium hydroxide, and combinations thereof; and the remaining beingwater; wherein the core particle is selected from the group consistingof silica, alumina, titania, zirconia, polymer particle, andcombinations thereof; and the nanoparticle is ≥10 nm and is selectedfrom the compounds of a group consisting of zirconium, titanium, iron,manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine,lanthanum, strontium nanoparticle, and combinations thereof; change ofsize distribution of composite particles under a disintegrative force isless than 10%; and the polishing composition has a pH of about 2 toabout
 12. 2. The polishing composition of claim 1 wherein the coreparticle is silica particle, the nanoparticle is ceria nanoparticle, andthe composite particles are ceria coated silica composite particles. 3.The polishing composition of claim 2 wherein the composite particles areamorphous silica ceria particles having surfaces covered by singlycrystalline ceria nanoparticles.
 4. The polishing composition of claim 1has a pH ranging from 4 to 10; and the change of size distribution ofcomposite particles under a disintegrative force is less than 5%.
 5. Thepolishing composition of claim 1 comprises ceria coated silica compositeparticles, the additive selected from the group consisting ofpolyacrylic acid (PAA) or salt, poly(methyl methacrylate) (PMMA), andcombinations thereof; ammonium hydroxide; has a pH ranging from 4.5 to7.5; and the change of size distribution of composite particles under adisintegrative force is less than 2%.
 6. The polishing composition ofclaim 1 further comprises a surfactant selected from the groupconsisting of a). non-ionic surface wetting agents; b). anionic surfacewetting agents; c). cationic surface wetting agents; d). ampholyticsurface wetting agents; and mixtures thereof; and a biological growthinhibitor selected from the group consisting of tetramethylammoniumchloride, tetraethylammonium chloride, tetrapropylammonium chloride,alkylbenzyldimethylammonium chloride with the alkyl chain ranges from 1to about 20 carbon atoms, alkylbenzyldimethylammonium hydroxide with thealkyl chain ranges from 1 to about 20 carbon atoms, sodium chlorite,sodium hypochlorite, and combinations thereof.
 7. A polishing method forchemical mechanical planarization of a semiconductor substratecomprising at least one surface having at least one oxide layer,comprising the steps of: a) contacting the at least one oxide layer witha polishing pad; b) delivering a polishing composition to the at leastone surface, the polishing composition comprising: composite particlescomprising core particles with surfaces covered by nanoparticles; anadditive selected from a compound having a functional group selectedfrom the group consisting of organic carboxylic acids, amino acids,amidocarboxylic acids, N-acylamino acids, and their salts thereof;organic sulfonic acids and salts thereof; organic phosphonic acids andsalts thereof; polymeric carboxylic acids and salts thereof; polymericsulfonic acids and salts thereof; polymeric phosphonic acids and saltsthereof; arylamines, aminoalcohols, aliphatic amines, heterocyclicamines, hydroxamic acids, substituted phenols, sulfonamides, thiols,polyols having hydroxyl groups, and combinations thereof; a pH-adjustingagent selected from the group consisting of sodium hydroxide, potassiumhydroxide, cesium hydroxide, ammonium hydroxide, quaternary organicammonium hydroxide, and combinations thereof; and the remaining beingwater; wherein change of size distribution of composite particles undera disintegrative force is less than 10%; the core particle is selectedfrom the group consisting of silica, alumina, titania, zirconia, polymerparticle, and combinations thereof; and the nanoparticle is selectedfrom the compounds of a group consisting of zirconium, titanium, iron,manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine,lanthanum, strontium nanoparticle, and combinations thereof; and thepolishing composition has a pH of about 2 to about 12; and c) polishingthe at least one oxide layer with the polishing composition.
 8. Themethod of claim 7, wherein the nanoparticle is ceria nanoparticle, thenanoparticle is ceria nanoparticle, and the composite particles areamorphous silica ceria particles having surfaces covered by singlycrystalline ceria nanoparticles.
 9. The method of claim 7, wherein thepolishing composition has a pH ranging from 4 to 10; and the change ofsize distribution of composite particles under a disintegrative force isless than 5%.
 10. The method of claim 7, wherein the polishingcomposition further comprises a surfactant selected from the groupconsisting of a). non-ionic surface wetting agents; b). anionic surfacewetting agents; c). cationic surface wetting agents; d). ampholyticsurface wetting agents; and mixtures thereof; and a biological growthinhibitor selected from the group consisting of tetramethylammoniumchloride, tetraethylammonium chloride, tetrapropylammonium chloride,alkylbenzyldimethylammonium chloride with the alkyl chain ranges from 1to about 20 carbon atoms, alkylbenzyldimethylammonium hydroxide with thealkyl chain ranges from 1 to about 20 carbon atoms, sodium chlorite,sodium hypochlorite, and combinations thereof.
 11. The method of claim7, wherein the polishing composition comprises ceria coated silicacomposite particles, the additive selected from the group consisting ofpolyacrylic acid (PAA) or salt, poly(methyl methacrylate) (PMMA), andcombinations thereof; ammonium hydroxide; has a pH ranging from 4.5 to7.5; and the change of size distribution of composite particles under adisintegrative force is less than 2%.
 12. The method of claim 7, whereinthe at least one oxide layer is a silicon oxide layer.
 13. The method ofclaim 7, wherein the polishing pad is a soft pad.
 14. The method ofclaim 13, wherein polishing removal rate for the at least one oxidelayer is equal or greater than 500 A/min.
 15. A system for chemicalmechanical planarization, comprising: a semiconductor substratecomprising at least one surface having at least one oxide layer; apolishing pad; and a polishing composition comprising: compositeparticles comprising core particles with surfaces covered bynanoparticles; an additive selected from a compound having a functionalgroup selected from the group consisting of organic carboxylic acids,amino acids, amidocarboxylic acids, N-acylamino acids, and their saltsthereof; organic sulfonic acids and salts thereof; organic phosphonicacids and salts thereof; polymeric carboxylic acids and salts thereof;polymeric sulfonic acids and salts thereof; polymeric phosphonic acidsand salts thereof; arylamines, aminoalcohols, aliphatic amines,heterocyclic amines, hydroxamic acids, substituted phenols,sulfonamides, thiols, polyols having hydroxyl groups, and combinationsthereof; a pH-adjusting agent selected from the group consisting ofsodium hydroxide, potassium hydroxide, cesium hydroxide, ammoniumhydroxide, quaternary organic ammonium hydroxide, and combinationsthereof; and the remaining being water; wherein change of sizedistribution of composite particles under a disintegrative force is lessthan 10%; the core particle is selected from the group consisting ofsilica, alumina, titania, zirconia, polymer particle, and combinationsthereof; and the nanoparticle is selected from the compounds of a groupconsisting of zirconium, titanium, iron, manganese, zinc, cerium,yttrium, calcium, magnesium, fluorine, lanthanum, strontiumnanoparticle, and combinations thereof; and the polishing compositionhas a pH of about 2 to about 12; and wherein at least one oxide layer isin contact with the polishing pad and the polishing composition.
 16. Thesystem of claim 15, wherein the nanoparticle is ceria nanoparticle, thenanoparticle is ceria nanoparticle, and the composite particles areamorphous silica ceria particles having surfaces covered by singlycrystalline ceria nanoparticles.
 17. The system of claim 15, wherein thepolishing composition has a pH ranging from 4 to 10; and the change ofsize distribution of composite particles under a disintegrative force isless than 5%.
 18. The system of claim 15, wherein the polishingcomposition further comprises a surfactant selected from the groupconsisting of a). non-ionic surface wetting agents; b). anionic surfacewetting agents; c). cationic surface wetting agents; d). ampholyticsurface wetting agents; and mixtures thereof; and a biological growthinhibitor selected from the group consisting of tetramethylammoniumchloride, tetraethylammonium chloride, tetrapropylammonium chloride,alkylbenzyldimethylammonium chloride with the alkyl chain ranges from 1to about 20 carbon atoms, alkylbenzyldimethylammonium hydroxide with thealkyl chain ranges from 1 to about 20 carbon atoms, sodium chlorite,sodium hypochlorite, and combinations thereof.
 19. The system of claim15, wherein the polishing composition comprises ceria coated silicacomposite particles, the additive selected from the group consisting ofpolyacrylic acid (PAA) or salt, poly(methyl methacrylate) (PMMA), andcombinations thereof; ammonium hydroxide; has a pH ranging from 4.5 to7.5; and the change of size distribution of composite particles under adisintegrative force is less than 2%.
 20. The system of claim 15,wherein the at least one oxide layer is a silicon oxide layer.
 21. Thesystem of claim 15, wherein the polishing pad is a soft pad.